Increasing network demands are driving the replacement of copper communications infrastructure with optical fiber. This process began at the continent scale with long-haul links. More recently, fiber has penetrated the metropolitan area networks (MANs) and the aggregation layers of large datacenters. With cloud computing driving demands on datacenter networks, optical communications has already begun to be implemented at the individual server level.
Traditionally, optical networks were wired statically; more recently, networks in which the geometry can be adapted have been implemented via several approaches. One approach employs reconfigurable add-drop multiplexers (ROADMs), which are used in wavelength division multiplexing (WDM) systems to add or remove one spectral component (at one single wavelength) while passing others. More recently, software defined networking has driven the adoption of more fluid physical architectures.
Existing architectures for optical switches are either based on microelectromechanical systems (MEMS) or collimators aided with piezoelectric drivers. These free-space switches are large, expensive, and usually include complex feedback systems to physically align the free-space optical paths internally.